shutdown no longer umounts idle USB connected drive.

Hi

I have a USB connected hard drive which powers down when idle. Recently 
(in the last 2 weeks or so) shutdown appears to have stopped waiting for 
the drive to spin up in order to cleanly unmount. I can perform a git 
bisect but the system is relatively slow so if anyone has a change in 
mind that might be the culprit, I can start around that point.

Ian